An "old bat" who takes on Tiffany Aching as apprentice three months prior to the events of Wintersmith. Many have come to the position before Tiffany, and she is the only one to not run away. Miss Treason uses two sticks to walk and is both deaf and blind, but manages to get along by Borrowing the senses of those around her. Perhaps her "creepiest" use of this talent is making whatever apprentice she has at the moment her "mirror" before they go out. She will have the poor dear stand in front of her and borrow her sight so that she can see herself from the girl's perspective. The girls who have experienced this say that the creepiest part is the tingling at the back of your eyes, something that anyone whose senses are being Borrowed experiences.

All witches specialise in one field or another, and Miss Treason's speciality is Justice, (in fact her name refers to the Eumenidies of Greek Myth, who came to represent Justice in the later myths.) People come to her to settle disputes, and usually find it very difficult to lie to her. This is most likely all in their heads, as Ms. Treason has a reputation as being very scary and also very powerful. It is said by the villagers that great kings and princes had come for miles just to ask her for her advice and to seek justice from her. Though the villagers fear her more than anything else, they also seem to hold great respect for her. Ms. Treason later explains to Tiffany that she knew the that villagers would never love her, and that the other option was to make them fear her: She decided they either had to fear her, or love her, so that she could hold some power over them.

One of the most notable things about Miss Treason's cottage is that everything in it is black, from the floor to the rafters. While Tiffany is her apprentice, she has to paint her cheeses with black-colored wax so that they'll fit in with the theme. Her cottage has all the hallmarks of a 'bad witch', (i.e. skulls, spider webs, etc.,) and all of which of these are fake, bought from Boffo's, a joke shop in Ankh-Morpork. Treason also uses the name "Boffo" to describe the unique power that these props give her: She describes "Boffo" as "the power of expectations;" the strength that one gains from behaving exactly as someone expects you to.

No witch actually has spiders' webs in her cottage or keeps skulls for any reason, but most simple folk expect witches to do so, and so Miss Treason obliges them; the better to ensure that when people come calling they don't see what is really there, (a tired, blind 111-year-old woman,) but what they expect, (a venerable, terrifying 113-year-old witch.) She also ensured that many of the rumours about her are kept current and circulating, to ensure the presence of "Boffo thinking" among her clients. One of the most prevalent rumours is that her heart had stopped many years ago and that the iron clock she carries at her waist is actually a mechanical heart.

Miss Treason dies of old age during the events of Wintersmith, but as she, like all witches, knows the date and time of her death, she was able to enjoy her funeral ceremony the day before. On the day of her death she comes out of her house to find: many Feegles who couldn't miss out on the ceremony, (or apparently keep their mouths shut about it,) a grave dug by said-Feegles, and many hysterical villagers, (who are primarily concerned with Ms. Treason solving their problems, which she does, even as she walks into the grave.) Mindful of her image to the very end, Miss Treason used the presence of the locals to give them one last show, (i.e. walking into the grave, stopping her clock with her thumbnail to imply her death.)

Tiffany, later, half-jests that continued visits by people to her grave may turn her into a goddess figure. This later comes to pass as, when Tiffany returns to the cottage, she sees that the villagers have been leaving pleas for help written on bits of paper around Miss Treason's grave, in the hope that she can help them from the beyond. Her cottage was then passed down to Annagramma Hawkin, who, after a decidedly shaky start, has begun to fulfill her role properly, with assistance from Tiffany and the Boffo's catalogue. She uses a green mask and feet props to convince people that she turns into a hideous monster when angered.